1. Field of the Invention
The present invention relates to an improvement of a force storing mechanism having a closing spring for a circuit breaker.
2. Discussion of Background
There is a requirement by a standard for the operation mechanism of a circuit breaker to have such a construction that the opening and closing of a circuit can be performed in succession without a delay. In order to meet the requirement of such standard, there is a conventional technique wherein a circuit closing operation is performed by the aid of an electric motor immediately after a circuit opening operation has been performed by using a mechanical energy stored in a force storing mechanism (a spring is generally used therein) so that energy is stored in the force storing mechanism for a successive circuit opening operation.
As a conventional mechanism for operating a circuit breaker, the construction and operation of the operation mechanism as disclosed in Japanese Unexamined Patent Publication JP-A-9-106741 (Japanese Patent Application JP7-264203) will be described.
FIG. 8 is a front view showing the construction of an operation mechanism of circuit breaker in its circuit-closing state; FIG. 9 is a cross-sectional view taken along a line A--A in FIG. 8; FIG. 10 is an enlarged view of a portion in FIG. 9; and FIG. 11 is a perspective view showing the detail of parts shown in FIG. 9. FIGS. 12a and 12b are diagrams showing the operations of the portion shown in FIG. 10. Throughout the Figures, expression showing directions of rotation are used on the basis of FIG. 8.
A lever 2 linked with a movable contact 100 (expressed by a sign of circuit in FIG. 8) is fixed to a main shaft 3 to which a rotating force is applied clockwise by a breaking spring 87 (expressed by a sign of spring), and is held in a closing position by a tripping latch 4. When the tripping latch 4 is turned counterclockwise by a tripping trigger mechanism 5, the lever 2 is turned counterclockwise to open the movable contact 100.
A gear wheel 9 is fixed to a cam shaft so as to rotate along with the cam shaft 8. A connecting pin 88 is provided on a side surface of the gear wheel 9. A closing lever 7 is fixed to a closing main shaft 6 to which a rotating force is applied counterclockwise by a closing spring (expressed by a sign of spring). A link 10 is provided to link the connecting pin 88 to an end portion of the closing lever 7. A lever crank mechanism (hereinafter, simply referred to as "mechanism") is formed by a crank formed between the center of the gear wheel 9 and the connecting pin 88; the link 10 as a connecting rod; and the closing lever 7 as a driver.
The gear wheel 9 is kept by a closing latch 11 at its closing awaiting position which is slightly shifted clockwise from a change point (an upper dead point) of the mechanism (i.e., a state shown in FIG. 8). When the closing latch 11 is turned counterclockwise by the actuation of a closing trigger mechanism 12, the closing lever 7 is turned counterclockwise and the gear wheel 9 is turned clockwise, respectively, by the mechanical energy stored in the closing spring 89. A cam 13 fixed to the cam shaft 8 together with the gear wheel 9 is rotated so that the lever 2 in its breaking position is returned to its closing position against the rotating force of the breaking spring 87 to thereby close the movable contact 100.
At the same time, a pinion 15 meshed with the gear wheel 9 is rotated counterclockwise through a clutch driving means 16 by the aid of an electric motor 17. Then, the gear wheel 9 is rotated clockwise against the rotating force of the closing spring 89 so as to return to the state shown in FIG. 8.
The above-mentioned elements are assembled with a frame 1 to form an operation mechanism. Among these elements, elements for transmitting a force from the electric motor 17 to the enclosing spring 89 via the clutch driving element 16, the pinion 15, the gear wheel 9, the link 10, the closing lever 7 and so on, constitute a force storing mechanism.
A clutch shaft 14 and the rotating shaft of the electric motor 17 are disposed in parallel to the cam shaft 8. These three shafts are connected in a form of a series of gear wheels comprising the gear wheel 9, the pinion 15 formed in an end of the clutch shaft 14, the clutch driving element 16 having a gear element (an outer ring 19) at its outer circumference and a gear formed in an end of the rotating shaft of the electric motor 17. The pinion 15 and the clutch driving element 16 constitute a clutch.
The cam shaft 8 penetrates frame walls 1a, 1b so that it is supported by a pair of bearings at the penetrating portions. A cam 13 is firmly fitted to the cam shaft 8 at an intermediate position between the frame walls 1a, 1b, and the gear wheel 9 on which a projection (an end-face cam) 9a is provided is firmly fitted to one of the free ends (which is at the side of the frame wall 1a) whereby the cam shaft 8 and the cam 13 are rotated in one-piece along with the rotation of the gear wheel 9. The cam shaft 8 is prevented from the movement in the axial direction beyond a play in the bearings.
The clutch shaft 14 also penetrates the frame walls 1a, 1b so that it is supported by a pair of bearings at penetrating portions in the frame walls 1a, 1b so as to be rotatable. The pinion 15 is provided at the end of the clutch shaft 14 at the side of the frame wall 1a. The clutch shaft 14 is allowed to move to some extent in the axial direction.
The clutch shaft 14 is provided with an inner wheel 18 at its outer circumference in the end portion at the side where the gear wheel 9 meshes with the pinion 15. Further, the clutch shaft 14 is provided with a hollow portion 14b at a center portion thereof having a cylindrical wall surface which is concentric with the inner wheel 18.
The pinion 15 comprises a toothed wheel portion 15a meshed with the gear wheel 9 and a shaft portion 15b integrally formed therewith. The shaft portion 15b is fitted rotatably in the hollow portion 14b of the cam shaft 8 through a stopper member 14c.
The inner wheel 18 is fitted to the clutch shaft 14 so as to be movable in the axial direction together with the clutch driving element 16. Radial grooves 18a are formed in an end portion (the end opposing the pinion 15) to be meshed with the toothed wheel portion 15 of the pinion 15.
FIG. 11 is a perspective view of the pinion 15 and the inner wheel 18 to clarify the structure of the inner wheel 18.
The traveling distance of the clutch driving element 16 is regulated by the height of the projection 9a provided on the gear wheel 9 so that the meshing engagement between the pinion 15 and the radial grooves 18a of the inner wheel 18 is disconnected in the state that the clutch driving element 16 is pressed by the projection 9a and is moved toward the frame wall. While the gear wheel 9 is rotated clockwise to an appropriate location from a position which is slightly shifted clockwise from the change point of the mechanism to the closing awaiting position, the projection 9a provided on the gear wheel 9 presses the clutch driving element 16 toward the frame wall to move the clutch shaft 14 by a predetermined distance whereby the meshing engagement between the pinion 15 and the radial grooves 18a of the inner wheel 18 is disconnected.
The clutch driving element 16 is composed of the inner wheel 18, the outer wheel 19 and a one-way clutch 20 provided between the inner wheel 18 and the outer wheel 19 wherein the inner wheel 18 is fitted to the clutch shaft 14 so as to be rotatable and movable in the axial direction. The outer surface of the inner wheel 18 is fitted to the one-way clutch 20.
The outer wheel 19 is meshed at an outer peripheral toothed wheel portion thereof with a toothed wheel portion 17a formed in the shaft end of the electric motor 17 and fitted at the inner diametrical surface thereof with the one-way clutch 20 so that it is mutually rotatable with respect to the inner wheel 18 while not causing a relative movement in the axial direction. The one-way clutch 20 is adapted such that it transmits a torque from the outer wheel 19 to the inner wheel 18 only when the outer wheel 19 is rotated counterclockwise with respect to the inner wheel 18 as seen from the side of the pinion 15. The tooth width of the toothed wheel portion 17a formed in the end of the shaft of the electric motor 17 is formed so as to always mesh with the clutch driving element 16 even when it is displaced by the projection 9a.
A clutch spring 21 is disposed between the frame wall 1a and the clutch driving element 16 so as to push continually the clutch driving element 16 toward the pinion 15.
The operation of the mechanism will be described. The operation for storing a mechanical energy in the closing spring 89 after the closing of the movable contact 100 is as follows.
The electric motor 17 is rotated clockwise and the clutch driving element 16 is rotated counterclockwise by the toothed wheel portion 17a formed at the shaft end of the motor. When the closing spring 89 has released the mechanical energy, the projection 9a formed on a side face of the gear wheel 9 is at a position apart from the clutch driving element 16. Accordingly, the clutch driving element 16 is pressed by the clutch spring 21 so that the pinion 15 and the radial grooves 18a formed in the end portion of the inner wheel 18 are meshed with each other whereby the pinion 15 can be driven by the electric motor 17 through the clutch driving element 16.
When the gear wheel 9 is rotated and has slightly passed clockwise the change point of the mechanism, the projection 9a presses the clutch driving element 16 to move it toward the frame wall 1b. As a result, the linkage between the pinion 15 and the clutch driving element is disconnected. At this moment, the electric motor 17 does not drive the pinion 15.
After the disengagement of linkage between the pinion 15 and the clutch driving element 16, the gear wheel 9 is further rotated clockwise by a small amount by the force of the closing spring 89, and is stopped at its closing awaiting position by the closing latch 11.
Since the linkage between the clutch driving element 16 and the pinion 15 is disconnected just before the point where the mechanism reaches the closing waiting position, a force due to the output torque of the electric motor 17 is not applied to the closing latch 11 even if the electric motor 17 rotates due to inertia after the stopping of the gear wheel 9.
FIG. 12 is a cross-sectional view showing a relation among the projection 9a, the outer wheel 19 and the gear wheel 9 shown in FIG. 10 for the purpose of explaining the problem in the above-mentioned conventional technique.
The projection 9a provided on a side face of the gear wheel 9 moves in the direction of arrow mark in FIG. 12a. Symbols X1 and X2 in FIG. 12b show respectively the position of the projection 9a in a state that the projection 9a begins to contact with the outer wheel 19 (namely, the clutch begins to disconnect) and the position of the projection 9a in a state that the outer wheel 19 has been pushed by the projection 9a so that it has finished the movement (toward the upper portion of the paper surface of the Figure).
Since the projection 9a is brought to contact with a gentle slope formed in the outer wheel 19, there is a fair fluctuation, between the position X1 and the position X2, depending on a position of a top portion of the projection 9a (a vertical position or a height) which is brought to contact with the outer wheel 19.
As understood from FIG. 10, the position of the top portion of the projection 9a varies not only depending on the height of the projection 9a but also a position of the gear wheel 9 in the axial direction, namely, a shift of the cam shaft 8 in the axial direction. Further, the position of the outer wheel 19 is influenced by a position of the pinion 15 in the axial direction (i.e., a position of the clutch shaft 14 movable in its axial direction). Accordingly, it is necessary that the above-mentioned fluctuation is absorbed by adjusting the height of the projection 9a so as to obtain correct operational positions X1, X2 of the clutch. In the conventional technique, there was a problem that the adjustment was difficult since a slight difference of height of the projection 9a caused a substantial change of angular position of the gear wheel 9, and the adjustment took much labor. Specifically, in the conventional force storing mechanism adapted to disconnect the clutch by pressing the outer wheel by means of the projection, there was produced a fluctuation in angular position of the gear wheel at the time of disconnection (or connection) of the clutch due to a fluctuation in the relative distance between the gear wheel and the outer wheel and a fluctuation in height of the projection, which resulted a reduction in the performance of a circuit breaker installing the force storing device therein. Accordingly, it was insufficient to merely adjust correctly the height of the projection to a regulated dimension, and it was necessary to finely adjust the height at an actually working site.